1. Field of the Invention
The invention is directed to a multiple-clutch device, such as a double-clutch device, for arrangement thereof in a drivetrain of a motor vehicle between a drive unit and a transmission, wherein the clutch device has a first clutch arrangement associated with a first transmission input shaft of the transmission and a second clutch arrangement associated with a second transmission input shaft of the transmission for transmitting torque between the drive unit and the transmission.
2. Description of the Related Art
A clutch device of this type is known, for example, from EP 0 931 951 A1. The clutch device serves to connect the drive of a motor vehicle with a multiple-speed shift transmission via two friction clutches which are preferably automatically actuated, wherein a disengagement or release system is allocated to each of these two friction clutches, so that the two friction clutches can be engaged or released independently from one another. A clutch disk of one of the two friction clutches is arranged on a central transmission input shaft so as to be fixed with respect to rotation relative to it, while a clutch disk of the other friction clutch engages at a second transmission input shaft so as to be fixed with respect to rotation relative to it, this second transmission input shaft, constructed as a hollow shaft, enclosing the central transmission input shaft. The known double-clutch is arranged with a fixed thrust plate of one friction clutch at a flywheel of an internal combustion engine. To this extent, the arrangement of the double-clutch in a drivetrain substantially corresponds to the arrangement of conventional (single)friction clutches in the drivetrain.
Double-clutch devices (called simply double-clutches) of the type mentioned above have attracted great interest recently and are generally formed of two wet or dry clutches which are switched alternately, possibly also with overlapping. Particularly in connection with a multiple-speed shift transmission, clutches of this type make it possible to carry out shifting processes between two respective transmission speeds of the transmission without interruption of tractive forces.
In principle, double-clutch devices make it possible for both clutches to be applied jointly in especially difficult starting processes, particularly those common in car racing. For this purpose, the accelerator pedal can be deflected to its stop, as the case may be, while the motor vehicle is kept essentially stationary at the same time by applying the maximum braking force until the clutch has reached its optimal transmission point. When the braking action is canceled at the moment of reaching the optimal transmission point, the vehicle is started with maximum acceleration. Starting processes of this kind are also considered for motor vehicles with a relatively weak engine under extreme starting conditions, for example, when starting on an obstruction; that is, they are not considered only for racing cars.
Obviously, starting processes of the type described above lead to high slippage with a correspondingly extensive development of heat. This presents the problem of carrying away this heat from the area of the friction clutch serving as starting clutch. Further, a correspondingly high wear of the friction clutch must be taken into account. Moreover, heating of the friction clutches is accompanied by changes in the coefficient of friction of the friction clutches, so that control of the release mechanisms of the two friction clutches, and therefore control of the two friction clutches relative to one another, can be appreciably impaired. Since inaccuracies or changes in the functional matching of the two friction clutches relative to one another caused by heat can have the result that a torque ratio not intended in the shifting process is applied to the transmission input shafts, shifting processes in the shift transmission can be subjected to load. The synchronization in the shift transmission can be overtaxed in this way, so that, in the worst case, the shift transmission can be damaged to the point of complete failure, apart from disadvantages with respect to efficiency which occur in any case. On the whole, mismatching between the two friction clutches caused by heat is incompatible with a problem-free torque transmission in shifting processes in the shift transmission without interruption of tractive force and without jerking during shifting.
Another problem area in a double-clutch device relates to starting processes carried out in opposition to an inclination, wherein the motor vehicle must be prevented from rolling backward, or those which are used when parking at the lowest possible speed, for example, for precise positioning of a motor vehicle in a parking space. The operating states mentioned above are referred to in technical circles as xe2x80x9chill-holdingxe2x80x9d and xe2x80x9ccreepingxe2x80x9d. Both starting processes have in common that the friction clutch serving as starting clutch is operated, sometimes without actuation of the accelerator, over a longer period of time with slip. Although the torques to be transmitted in such starting processes lie well below those occurring under the operating conditions described above, especially in car racing, an intensive heating of the respective friction clutch or even both friction clutches can occur, resulting in the problems detailed above.
Suggestions have been made for gear-shifting strategies and shifting processes for double-clutch transmissions based on the aimed for adjustment of clutch slip (DE 196 31 983 C1) with consequent generation of friction heat. Depending on driving behavior, overheating problems of the type mentioned above cannot be ruled out.
The risk of intensive overheating exists not only in a dry friction clutch, but can also occur in so-called xe2x80x9cwetxe2x80x9d friction clutches, possibly in the form of a disk or plate clutch, which are operated by the action of a viscous operating medium such as hydraulic fluid. By way of example, a gear change box with two plate clutches is known from DE 198 00 490 A1, wherein one plate clutch is provided for forward driving and the other for driving in reverse. DE 198 00 490 A1 is concerned primarily with providing adequate cooling of the two plate clutches using the viscous operating medium. In spite of the liquid cooling, heating of the friction clutches is also a considerable problem in plate clutches because the operating medium, which usually flows through friction facing grooves or the like to carry off the heat, cannot be guided between the plates in optimal quantity. The reason for this is that, on one hand, excessive flow through the friction facing grooves or the like would build up a counterpressure between the friction surfaces of two adjacent plates and would therefore reduce the capacity of the friction clutches to transmit torque (with a corresponding increase in slip and therefore additional generation of friction heat, so that the problem of overheating is exacerbated) and, on the other hand, the operating medium could be overheated and destroyed when flowing through between the plates. Overheating in plate clutches can result in that the friction surfaces can no longer separate from one another completely during a disengaging process and, consequently, torques can still be transmitted via the clutch which should be disengaged, so that considerable drag torques can reach the associated shift transmission. When plate clutches are used in a multiple-clutch device, especially a double-clutch device, of the type mentioned above, shifting processes could again be brought under load in the shift transmission with resulting overtaxing of the synchronization in the shift transmission.
One approach to mastering overheating problems in the area of friction clutches in case of unfavorable operating conditions, for example, with problematic starting processes in a motor vehicle, is to provide another starting element in addition to the first and second clutch arrangements which is in the form of a hydraulic clutch or hydrodynamic clutch and comprises a hydrodynamic circuit with an impeller wheel, a turbine wheel and, if desired, a stator wheel. The driving member can be connected in parallel with one of the two friction clutches; that is, it can act on a common transmission input shaft irrespective of the engagement state of this friction clutch. A clutch device in which two plate clutches and a starting element of this type are integrated, was described in the German Patent Application 199 46 857.5 by the present Applicants which was applied for on Sep. 30, 1999 and whose disclosure is incorporated in the subject matter disclosed in the present application.
Within the framework of investigations undertaken by the present Applicants in connection with double-clutch devices, it was shown in general that wet-type clutches exhibit sealing problems and problems relating to output losses. Further, it was shown that boundary conditions relating to the available axial and radial installation space could be adhered to only with difficulty, if at all, based on the previously known concepts. With regard to clutches, possibly, diaphragm clutches, which are actuated by pistons integrated in the clutch device, the arrangement of the piston chambers associated with the pistons proved especially problematic.
It is the object of the invention to achieve improvements with respect to at least one of the problems mentioned above and/or other problems.
According to a first independent aspect of the invention, for a multiple-clutch device, such as a double-clutch device, for arranging in a drivetrain of a motor vehicle between a drive unit and a transmission, which clutch device has a first clutch arrangement associated with a first transmission input shaft of the transmission and a second clutch arrangement associated with a second transmission input shaft of the transmission for transmitting torque between the drive unit and the transmission, it is suggested that at least one of the clutch arrangements is constructed as a plate clutch arrangement and has an actuating piston defining a pressure chamber for actuation, preferably for engagement, of the plate clutch arrangement by means of a pressure medium, preferably hydraulic medium, wherein cooling fluid, e.g. cooling oil, can be supplied to the plate clutch arrangement from a cooling fluid supply. According to the invention, it is further suggested that the actuating piston, and also, if desired, a plate carrier, possibly an outer plate carrier, has at least one pressure compensation opening and/or cooling fluid outlet opening in a radial outer and/or central area. The reason for this step is that when the only outlet provided for the cooling fluid is through the area of the plates a certain accumulation of cooling fluid in a radial outer area of the clutch device next to the actuating piston can hardly be avoided at least when larger amounts of cooling fluid are supplied to the at least one plate clutch arrangement, for instance, during slip states with corresponding heat development (for example, when starting). In this case, forces based on an interaction between the actuating piston and cooling fluid can then act upon the actuating piston, especially, for example, forces caused by centrifugal force or hydrodynamic forces. Considered in general, pressure differences can occur between the two sides of the piston for different reasons which impede the engagement and/or disengagement of the associated clutch arrangement. Such impairments of the actuating piston are prevented or at least appreciably reduced by the proposed step.
In order to ensure a sufficient flow of cooling fluid through the plates in spite of the possibility for cooling fluid to flow out through the pressure compensation opening and/or cooling fluid outlet opening, according to the invention, while circumventing the plates, a conducting element can be provided adjacent to the pressure compensation opening and/or cooling fluid outlet opening, which conducting element reinforces a flow of cooling fluid through the plates. A particularly advantageous and space-saving suggestion in this respect consists in that the conducting element is formed by an axial outer plate of the plate clutch arrangement having a fluid-conducting portion.
A particularly preferred construction is characterized in that the plate carrier and the actuating piston are alternately cut out in circumferential direction so that they can engage one inside the other such that, in at least one stroke position of the actuating piston, at least one area of the actuating piston that is not cut out engages in at least one cutout of the plate carrier preferably serving as a pressure compensation opening and/or cooling fluid outlet opening and/or at least one area of the plate carrier that is not cut out engages in at least one cutout of the actuating piston preferably serving as a pressure compensation opening and/or cooling fluid outlet opening. This construction is also advantageous regardless of whether or not at least one pressure compensation opening and/or cooling fluid outlet opening is provided according to the invention because it makes it possible to economize on axial installation space. However, the cutouts are generally open in both axial directions, that is, they are constructed as through-openings, so that the plate carrier and the actuating piston can engage in one another such that the one is penetrated by the other. The cutouts which are continuous in axial direction also compulsorily serve as pressure compensation opening and/or cooling fluid outlet opening.
The first clutch arrangement as well as the second clutch arrangement are preferably constructed as plate clutch arrangements. It is suggested for this purpose that a plate carrier of the first clutch arrangement having plates with a larger friction radius and an actuating piston associated with this clutch arrangement are alternately cut out in circumferential direction so as to allow the plate carrier and actuating piston to engage one inside the other and/or wherein a plate carrier of the second clutch arrangement having plates with a smaller friction radius and an actuating piston associated with this clutch arrangement are alternately cut out in circumferential direction so as to allow the plate carrier and actuating piston to engage one inside the other. This results in the above-mentioned advantages with respect to economizing on axial installation space, wherein it is suggested by way of further development for a particularly compact construction of the clutch device that the actuating piston of the first clutch arrangement and the plate carrier of the second clutch arrangement are alternately cut out in circumferential direction so that they can engage one inside the other such that, in at least one stroke position of the actuating piston, at least one area of the actuating piston that is not cut out engages in at least one cutout of the plate carrier, which cutout preferably serves as a pressure compensation opening and/or cooling fluid outlet opening and/or at least one area of the plate carrier that is not cut out engages in at least one cutout of the actuating piston, which cutout preferably serves as a pressure compensation opening and/or cooling fluid outlet opening.
In general, it is provided for this purpose that the mutual engagement is given for every stroke position of the respective actuating piston in order to prevent the actuating piston from rotating relative to the respective plate carrier. For this purpose, a defined rotational play can be provided between the respective piston and the respective plate carrier; however, the components mentioned above can also be carried out with respect to one another in such a way that no significant relative play can occur between them. For the sake of completeness, however, it should also be noted that it can be provided in general that the pistons can be rotatable relative to the plate carriers or that one of the pistons can be rotatable relative to an associated plate carrier or both plate carriers. The pistons or piston can then be used as a damping mass.
According to a second independent aspect of the invention, for a multiple-clutch device, such as a double-clutch device, for arranging in a drivetrain of a motor vehicle between a drive unit and a transmission, which clutch device has a first clutch arrangement associated with a first transmission input shaft of the transmission and a second clutch arrangement associated with a second transmission input shaft of the transmission for transmitting torque between the drive unit and the transmission, it is suggested that at least one of the clutch arrangements is constructed as a plate clutch arrangement, wherein cooling fluid, such as cooling oil, can be supplied to the plate clutch arrangement from a cooling fluid supply, wherein at least one wall which shields an interior space of the clutch device and which is arranged in a torque transmission path between an input side of the clutch device and an output side of one of the clutch arrangements has, in a radial outer area and/or central area, at least one pressure compensation opening and/or cooling fluid outlet opening. Unwanted effects which are mediated through the cooling fluid and might possibly interfere with the engagement and/or disengagement of the plate clutch arrangement can accordingly be prevented or reduced. The preceding remarks relating to the first aspect of the invention apply in a corresponding manner.
The wall can comprise a plate carrier, particularly an outer plate carrier, having at least one pressure compensation opening and/or cooling fluid outlet opening. Reference is had to the inventive suggestion according to the first aspect and the accompanying descriptions.
The inventive idea can also be applied to other parts of the multiple-clutch device, for example, to a wall portion which is used for transmission of torque between a plate carrier and an input side of the clutch device, such as a clutch device hub, and which, according to the invention, then has at least one pressure compensation opening and/or cooling fluid outlet opening and which is part of the wall. A conducting element reinforcing a flow of the cooling fluid through the plates can be provided axially adjacent to the pressure compensation opening and/or cooling fluid outlet opening of the wall portion. The conducting element can be formed by an axial outer plate of the plate clutch arrangement having a fluid conducting portion. A portion of the wall portion located farther outward radially relative to the pressure compensation opening and/or cooling fluid outlet opening can also come under consideration as a conducting element.
With respect to the pressure compensation opening and/or cooling fluid outlet opening according to the first or second aspect of the invention, it should be added generally that this portion of the actuating piston or plate carrier or wall which generally extends in radial direction can be provided so that cooling fluid can flow through the opening essentially in axial direction. The pressure compensation opening and/or cooling fluid outlet opening according to the invention is another opening in addition to openings which may possibly be provided in the plate carriers to enable a cooling fluid flow through the plate stack and contributes at most secondarily, if at all, to the flow of cooling fluid flowing through the plate stack.
According to a third independent aspect of the invention, for a multiple-clutch device, such as a double-clutch device, for arranging in a drivetrain of a motor vehicle between a drive unit and a transmission, which clutch device has a first clutch arrangement associated with a first transmission input shaft of the transmission and a second clutch arrangement associated with a second transmission input shaft of the transmission for transmitting torque between the drive unit and the transmission, it is suggested that the first clutch arrangement and the second clutch arrangement are both constructed as plate clutch arrangements, wherein cooling fluid, such as cooling oil, can be supplied to the plate clutch arrangements from a cooling fluid supply, wherein a cooling fluid path to the plates of one of the clutch arrangements extends through at least one fluid passage opening in a wall portion of a plate carrier, possibly an inner plate carrier, of the other clutch arrangement, which wall portion connects a plate carrier hub with a plate retaining portion, and/or a fluid-conducting arrangement is provided for reinforcing a cooling fluid flow through a plate stack of at least one of the clutch arrangements.
According to this inventive idea, it is possible to supply both plate clutch arrangements with a sufficient quantity of cooling fluid, wherein it is also possible to supply a particularly large flow of cooling fluid to one of the two clutch arrangements which serves, for example, as a starting clutch or is operated with regulated slip, so that it must be ensured that friction heat is carried off in a particularly effective manner. This also holds true when a radial outer clutch arrangement of the first and second clutch arrangements surrounds a radial inner clutch arrangement annularly. In this case, it is preferred that the plate carrier having the fluid passage opening belongs to the radial inner clutch arrangement. A larger portion of the available cooling fluid can then flow past the inner clutch arrangement in order to cool the outer clutch arrangement in a particularly effective manner.
The fluid-conducting arrangement can contribute in an especially effective manner to ensure a sufficient cooling of the plates of the clutch arrangements. The fluid-conducting arrangement can comprise a conducting element which is formed by a plate of the respective plate clutch arrangement having a fluid-conducting portion. Further, it is suggested that the fluid-conducting arrangement comprises a wall which shields, at least in some areas, an interior space of the clutch device and which is arranged in a torque transmission path between an input side of the clutch device and an output side of one of the clutch arrangements. The wall can comprise a plate carrier, possibly an inner plate carrier, of the respective plate clutch device (whose plates are to be supplied with cooling fluid with the cooperation of the fluid-conducting arrangement) and/or of the other plate clutch device. Further, it is possible that the wall comprises a wall portion used for transmission of torque between a plate carrier and the input side of the clutch device. Other components of the multiple-clutch device can also perform a fluid-conducting function in the sense described above, for example, a wall of a pressure chamber, a wall of a pressure compensation chamber or even an actuating piston.
According to a fourth independent aspect of the invention, for a multiple-clutch device, such as a double-clutch device, for arranging in a drivetrain of a motor vehicle between a drive unit and a transmission, which clutch device has a first clutch arrangement associated with a first transmission input shaft of the transmission and a second clutch arrangement associated with a second transmission input shaft of the transmission for transmitting torque between the drive unit and the transmission, it is suggested that at least one of the clutch arrangements is constructed as a plate clutch arrangement to which cooling fluid, such as cooling oil, can be supplied by a cooling fluid supply, possibly a cooling oil supply, wherein a plate stack of the plate clutch arrangement has metal plates, such as steel plates, having no facing and plates having friction facings and an inner plate carrier and an outer plate carrier of the plate clutch arrangement are constructed for allowing at least one flow of cooling fluid to enter between plates of the plate stack from the radial inner side in such a way that, at least in one operating state of the clutch arrangement, the cooling fluid flows directly against steel plates having no facing and/or plates having a sintered facing and flows directly along the latter in radial outward direction.
It is achieved by means of the inventive suggestion that the plates which, because of the way they are constituted, absorb friction heat and store it temporarily depending on their heat capacity (plates with friction facings made of thermally insulating material, e.g., paper material, are capable of this only to a comparatively slight degree at best) and which consequently provide at least a majority of the available heat capacity interact with the cooling fluid so that this heat can be effectively absorbed by the plates and therefore guided away so that effective cooling is provided as a result. For this purpose, a passage opening of the inner plate carrier which overlaps an axial area occupied by the respective plate when the clutch arrangement is engaged can be allocated to the respective metal plate or the plate having the sintered facing against which the flow is directed. Alternatively, the passage opening can overlap the axial area occupied by the respective plate when the clutch arrangement is disengaged when a particularly effective dissipation of heat is to be effected by utilizing the heat buffer function of the plate in the disengaged state of the clutch arrangement. The passage opening preferably overlaps the axial area occupied when the clutch arrangement is engaged, as well as the axial area of the respective plate occupied when the clutch arrangement is disengaged, in order to provide for good heat dissipation in both states of the clutch arrangement.
At least one passage opening of the outer plate carrier can be allocated to the respective metal plate or the plate having the sintered facing, respectively, against which the cooling fluid flows; if desired, the passage opening is offset relative to the axial area occupied by the respective plate when the clutch arrangement is engaged and/or when the clutch arrangement is disengaged.
Generally, it is advantageous when passage openings in the inner plate carrier which are associated with different plates are offset relative to one another in circumferential direction and/or when passage openings in the outer plate carrier which are associated with different plates are offset relative to one another in circumferential direction. Every plate can then have at least one passage opening of sufficient size uniquely allocated to it in the respective plate carrier.
According to a fifth independent aspect of the invention, for a multiple-clutch device, such as a double-clutch device, for arranging in a drivetrain of a motor vehicle between a drive unit and a transmission, which clutch device has a first clutch arrangement associated with a first transmission input shaft of the transmission and a second clutch arrangement associated with a second transmission input shaft of the transmission for transmitting torque between the drive unit and the transmission, it is suggested that at least one of the clutch arrangements is constructed as a plate clutch arrangement to which cooling fluid, such cooling oil, can be supplied by a cooling fluid supply, wherein an inner plate carrier and an outer plate carrier and optionally further components of the plate clutch arrangement are constructed so as to allow at least a flow of cooling fluid to enter between plates of the plate stack from the radial inner side and flow out from the plate stack such that forces are exerted on the plates through the intermediary of the cooling fluid which act in favor of a disengagement of the plate clutch arrangement.
By reinforcing the release of the plate clutch arrangement by mediation of the cooling fluid, inertial forces which might oppose a quick release are more quickly overcome, so that the clutch device responds more quickly. This is advantageous, for example, when the plate clutch arrangement is operated with regulated slip.
The reinforcement of the releasing movement delivered by mediation through the cooling fluid is particularly advisable insofar as it frequently happens that the clutch arrangement can be released quickly (for example, as was mentioned, when the clutch arrangement is to be operated with regulated slip). Various factors can work against a quick release, for example, inertial forces which are exerted on the piston by a fluid coolant, especially cooling oil, or inertial forces which are mediated by the cooling fluid and act on the piston or which are based on the mass moment of inertia; as a rule, these inertial forces are particularly prominent when the piston releasing movement is introduced. For this reason, it is useful to reinforce the introduction of the piston releasing movement in the suggested manner above all.
In order to achieve reinforcement of the release of the plate clutch arrangement, a passage opening in the inner plate carrier and a passage opening in the outer plate carrier which allow flow through the plate stack can be offset relative to one another in such a way that the cooling fluid flowing through the plate stack is deflected in axial direction, preferably after the cooling fluid has flowed in radial direction between adjacent plates.
Forces acting in favor of a release of the plate clutch arrangement by mediation of the cooling fluid can be achieved, for example, in both of the following ways. Counterforces (reaction forces) occurring during the deflection of the cooling fluid can be utilized. Further, a drag effect of the deflected fluid can be utilized. The latter is preferred. For this purpose, it is suggested that at least the majority of the fluid flowing through the plate stack is deflected in the direction of an actuating piston of the respective plate clutch arrangement in order to achieve a drag effect of the fluid on the plates in the direction of the actuating piston and accordingly in favor of a release.
It is specifically suggested in this connection that at least one cooling fluid flow path passing the inner plates and the outer plates is provided radially between the inner plates of the plate stack and the outer plate carrier and/or radially between the outer plates of the plate stack and the inner plate carrier, wherein at least one axial positive flow of cooling fluid occurs predominantly in the direction of an actuating piston of the respective plate clutch arrangement * during operation when cooling fluid is supplied to the plate stack in order to exert a drag effect on at least some of the plates for releasing the plate clutch arrangement. In this regard, it is particularly useful when cooling fluid can flow out of the cooling fluid flow path in a first axial direction to an actuating piston and so as to pass an end plate on the actuating piston side and, when a cooling fluid flow path is provided radially between the outer plates of the plate stack and the inner plate carrier, preferably in addition to outlet possibilities, cooling fluid can flow in radial direction between adjacent plates of the plate stack and, when a cooling fluid flow path is provided radially between the inner plates of the plate stack and the outer plate carrier, if desired, in addition to outlet possibilities, cooling fluid can flow in radial direction through passage openings in the outer plate carrier. Further, it is particularly useful in this regard when cooling fluid can flow out of the cooling fluid flow path in a second axial direction opposed to the first axial direction to a counter-bearing which is associated with the actuating piston and at which the plate stack acted upon by the actuating piston can be supported, no cooling fluidxe2x80x94passing an end plate on the side of the counter-bearingxe2x80x94can flow out, or when only less cooling fluid can flow outxe2x80x94passing the end plate on the counter-bearing sidexe2x80x94than in the direction of the actuating piston so as to pass the end plate on the actuating piston side. The steps mentioned above, by themselves or in combination, cause any counterforces which act opposite to the drag effect of the fluid toward a release due to the deflection of the fluid (counterforces caused by the deflecting process itself) to dominate and cause forces which act on the whole toward a release to be exerted on the plates.
According to a sixth independent aspect of the invention, for a multiple-clutch device, such as a double-clutch device, for arranging in a drivetrain of a motor vehicle between a drive unit and a transmission, which clutch device has a first clutch arrangement associated with a first transmission input shaft of the transmission and a second clutch arrangement associated with a second transmission input shaft of the transmission for transmitting torque between the drive unit and the transmission, it is suggested that at least one of the clutch arrangements is constructed as a plate clutch arrangement having a plate stack in which plates which are associated with the drive unit and which are in a torque-transmitting connection or can be brought into a torque-transmitting connection with the clutch device via an input side of the clutch device can be brought into a frictional engagement with plates which are associated with one of the transmission input shafts and which are in a torque-transmitting connection or can be brought into a torque-transmitting connection with the clutch arrangement via an output side of the clutch arrangement, wherein cooling fluid, such as cooling oil, can be supplied to the plate stack by a cooling fluid supply, wherein at least some of the plates associated with the drive unit have flow passages which make it possible for cooling fluid to flow through the plate stack, generally from the radial inner side to the radial outer side, when the plates are in frictional engagement.
Since the plates having flow passages are provided on the drive unit side, these plates are driven in rotation continuously (or at least more frequently or for longer periods of time than the plates on the transmission side) when the drive unit is running. The revolving flow passages cause a feeding effect with respect to the cooling fluid, which leads to a better distribution of the cooling fluid in the plate stack and a continuous (or at least more regular) cooling fluid flow through the plate stack resulting in improved cooling action.
The flow passages preferably comprise passages which are formed by surface structures of a respective friction surface. For example, the plates associated with the drive unit can have friction facings which are formed of paper material or sintered material, if desired, wherein the passages can be constructed, for example, in the form of facing grooves or other surface structures. In general, it is suggested that flow passages are formed in the friction facings. The plates associated with the drive unit are preferably outer plates.
The features of a multiple-clutch and a drivetrain which were indicated in connection with the different aspects of the invention can be advantageously combined. Further independent aspects of the invention will be discerned by the person skilled in the art from the preceding explanations and the description of the Figures.
The invention is further directed to a drivetrain for a motor vehicle with a clutch device, according to at least one aspect of the invention, arranged between a drive unit and a transmission.
The invention will be described more fully in the following with reference to embodiment examples shown in the Figures.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.